init: Mark all of inits children and init itself as important

This is based on a fragment of Guillem Jovers patch presented here:

http://lists.gnu.org/archive/html/bug-hurd/2006-02/msg00081.html

It has been refreshed, updated and the copyright year is adjusted
properly. It has been complemented with the necessary features to
address the issues the original patch set out to address, namely
that killall5 freezes the proc translator before it tries to walk
over /proc/*/stat to decide which process to kill. Prior to this
patch (and the one marking the procfs server as important
process), killall5 would deadlock trying to walk over the proc
file system.

Ironically it would not have killed any process later on even if
it had the chance, since two values obtained from /proc/*/stat
are currently hardcoded to zero in our procfs. Patches addressing
the problem as a whole are prepared and will be sent as a follow
up.

* init/init.c (launch_core_servers): Mark init, auth, proc and fs
  servers as important.
(start_child): Mark the real init as important.
(S_startup_important_task): Mark exec server as important.

1 files changed, 17 insertions, 4 deletions

diff --git a/init/init.c b/init/init.c
index 05fce78f..94f1a9bc 100644
--- a/init/init.c
+++ b/init/init.c
@@ -1,7 +1,7 @@
 /* Start and maintain hurd core servers and system run state
 
    Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
-     2005, 2008 Free Software Foundation, Inc.
+     2005, 2008, 2013 Free Software Foundation, Inc.
    This file is part of the GNU Hurd.
 
    The GNU Hurd is free software; you can redistribute it and/or modify
@@ -643,6 +643,8 @@ launch_core_servers (void)
       device_master = 0;
     }
 
+  /* Mark us as important.  */
+  proc_mark_important (procserver);
   proc_mark_exec (procserver);
 
   /* Declare that the filesystem and auth are our children. */
@@ -650,6 +652,7 @@ launch_core_servers (void)
   proc_child (procserver, authtask);
 
   proc_task2proc (procserver, authtask, &authproc);
+  proc_mark_important (authproc);
   proc_mark_exec (authproc);
   startup_authinit_reply (authreply, authreplytype, 0, authproc,
 			  MACH_MSG_TYPE_COPY_SEND);
@@ -672,6 +675,7 @@ launch_core_servers (void)
   err = proc_task2proc (procserver, proctask, &procproc);
   if (!err)
     {
+      proc_mark_important (procproc);
       proc_mark_exec (procproc);
       mach_port_deallocate (mach_task_self (), procproc);
     }
@@ -681,6 +685,7 @@ launch_core_servers (void)
   /* Get the bootstrap filesystem's proc server port.
      We must do this before calling proc_setmsgport below.  */
   proc_task2proc (procserver, fstask, &fsproc);
+  proc_mark_important (fsproc);
   proc_mark_exec (fsproc);
 
 #if 0
@@ -785,8 +790,10 @@ frob_kernel_process (void)
       return;
     }
 
-  /* Mark the kernel task as an essential task so that we never
-     want to task_terminate it.  */
+  /* Mark the kernel task as an essential task so that we or the proc server
+     never want to task_terminate it.  */
+  proc_mark_important (proc);
+
   err = record_essential_task ("kernel", task);
   assert_perror (err);
 
@@ -1067,6 +1074,7 @@ start_child (const char *prog, char **progargs)
 		   default_ports, MACH_MSG_TYPE_COPY_SEND, INIT_PORT_MAX,
 		   default_ints, INIT_INT_MAX,
 		   NULL, 0, NULL, 0);
+  proc_mark_important (default_ports[INIT_PORT_PROC]);
   mach_port_deallocate (mach_task_self (), default_ports[INIT_PORT_PROC]);
   mach_port_deallocate (mach_task_self (), file);
   if (err)
@@ -1207,7 +1215,12 @@ S_startup_essential_task (mach_port_t server,
       if (!strcmp (name, "auth"))
 	authinit = 1;
       else if (!strcmp (name, "exec"))
-	execinit = 1;
+        {
+          execinit = 1;
+          mach_port_t execproc;
+          proc_task2proc (procserver, task, &execproc);
+          proc_mark_important (execproc);
+        }
       else if (!strcmp (name, "proc"))
 	procinit = 1;